Airbags basically consist of a folded cushion that is quickly inflated by means of a gas produced by a generator when certain sensor devices detect a collision of the vehicle. The cushion is thus deployed in front of the driver or a passenger, depending on the location thereof, and prevents their bodies from hitting against any area of the vehicle.
In normal cushion deployment operation, the internal pressure produced by the generator when the cushion is filled with gas may be high enough to cause the cushion to be so hard that the occupant bounces off it. To prevent this drawback, they have been provided with a venting opening serving to reduce internal pressure of the cushion and, accordingly, the possibility of causing damage when they are activated.
The use of several means of blocking this venting opening to achieve a better control of the internal pressure in the cushion than that provided by only the variation of the size of the opening is in turn known. In this sense, the use of patches for achieving that the gas does not exit the discharge opening immediately but rather when the patch breaks as a given pressure inside the cushion has been reached, must be pointed out. The art has proposed different types of patches with different means for controlling the breaking thereof, more or less according to a certain resistance to the gas pressure inside the cushion. The presence of the gas pressure required for the cushion to carry out its protective function is thus made compatible with the assurance that the gas pressure will not reach an excessive value, with the risk for the people for whom the cushion is deployed.
Additionally, venting devices that allow increasing the gas outlet flow according to the specific characteristics of each collision and the type of passenger involved have also become necessary, and to that effect several venting device solutions providing adjustable surface venting openings facilitating the increase of the venting area as the internal pressure in the cushion increases are also known.
A newly arisen need involves the need for airbags that allow reducing the venting area, even completely eliminating it, in certain impact conditions, which requires closing mechanisms that must function in the sense opposite to the art known up until now. The traditional previously mentioned patches had to completely seal the outlet opening until the internal gas pressure inside the cushion did not reach a given level and then they broke, no longer functioning; now the opposite is required: devices that allow closing the venting opening when it is already open when the internal pressure of the cushion reaches certain levels.
Spanish patent ES 2,182,629, U.S. Pat. No. 6,139,048, patent applications US 2004/0090054, WO 2006/024472, WO 2006/136206 and US 2006/0151979 describe devices using moving elements to close the venting opening using the stresses produced in the cushion due to the pressure difference together with the difference of how the occupant strikes the airbag.
Notwithstanding the foregoing, the automotive industry constantly demands venting regulation devices that can meet the growing needs of airbags to adapt to the conditions of the impact and to the features of the vehicle occupant to be protected.